Thursday, September 13, 2012

Denisovan Gene Sequencing

What the fossil record shows about Denisovans: They had at least one finger, one toe, and a tooth.

This evidence comes from the Denisova Cave in Siberia.Scientists found the finger, toe, and tooth, which came from three different individuals, in different levels of the cave, and after doing a DNA analysis determined that their last common ancestor with humans lived about a million years ago. (The fossils dated from about 50,000 years ago). Of course, with such a minimal amount of material available, it's a bit tricky to get a complete gene sequence. The fact that the cave is in Siberia helps some (the average temperature in the cave is right around freezing) but some nice work on sequencing from a group led by Matthias Meyer helped as well.

Here's what they did to the source material:

DNA is dephosphorylated, heat denatured, and ligated to a biotinylated adaptor oligonucleotide, which allows its immobilization on streptavidincoated beads.

I'm sure you're kicking yourself for not thinking of it first. At any rate, the immobilization of the DNA on the beads seems to be the important part, as it allows for copying of the sequence thus creating extra source material to work with. We now know more about Denisovan gene seqences than we do about Neanderthal sequences, as the quality of these Denisovan genes is better, less contaminated, than anything we have from the Neanderthals. Pretty cool stuff! Here's an article from Ars Technica if you don't feel like wading through the original paper.